Mark A. Probert (February 5, 1907 - February 22, 1969) was an American trance medium and mental medium, billing himself as "A Telegnostic from San Diego", who acted as a channel of the Inner Circle (or Kethra E Da, Teachers of Light, as it is called in the Yuga language of E Yada Di Shi'ite). Records of Probert's seances were first published by Meade Layne and circulated as part of the BSRA's "Round Robin", forming the core of the earliest research into the Ether Ship Mystery.